Messages in this thread | | | Date | Tue, 20 Jan 2004 09:49:39 -0800 | From | Andy Lutomirski <> | Subject | Re: CPU Hotplug: Hotplug Script And SIGPWR |
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Tim Hockin wrote:
> On Tue, Jan 20, 2004 at 05:43:59PM +1100, Nick Piggin wrote: > >>>I think the sanest thing for a CPU removal is to migrate everything off the >>>processor in question, move unrunnable tasks into TASK_UNRUNNABLE state, >>>then notify /sbin/hotplug. The hotplug script can then find and handle the >>>unrunnable tasks. No SIGPWR grossness needed. >>> >> >>Seems less robust and more ad hoc than SIGPWR, however. > > > Disagree. SIGPWR will kill any process that doesn't catch it. That's > policy. It seems more robust to let the hotplug script decide what to do. > If it wants to kill each unrunnable task with SIGPWR, it can. But if it > wants to let them live, it can.
This seems like a problem that a lot of power-management issues have. (At some point, linux may want to suspend itself after inactivity. Both RT tasks and some interactive tasks may want to supress that.) Why not add a SIGPM signal, which is only sent if handles, and which indicates that PM event is happening. Give usermode some method of responding to it (e.g. handler returns a value, or a new syscall), and let /sbin/hotplug handle events for tasks that either ignore the signal or responded that they were uninterested. This seems be close to optimal for every case I can think of.
--Andy
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